Low-Power, High-Agility Space Robotics

Abstract

Control-moment gyroscopes (CMGs) have been used for attitude control on spacecraft that require large torques. We propose them for use in multibody robotic systems where high agility (or dexterity) and low power are important design goals. The architecture we propose offers singularity-free, reactionless slewing of a multi-joint robotic arm. It promises one to two orders of magnitude reduction in electromechanical power over otherwise identical systems with traditional joint drives or reactionless rotors. In broad terms, this improvement is possible because the CMGs transfer momentum with only small changes in kinetic energy. The large torques with which CMGs are associated are, in fact, constraint torques if the bodies are rigidly connected. They do no work, and they therefore require no input power per se. We describe the implementation of this concept on a small, free-flying spaceraft-maintenance robot (proposed by Princeton Satellite Systems), where 2 rad/sec rate, 2 rad/sec acceleration, and 2 rad/sec jerk are achieved for less than 1 kW peak power.